After sitting on the spark-plug fence for a while, I concur with Tony here. I think it makes sense to use the plug the system was originally designed for.
Designed for? We are just pumping a bunch of voltage and making it spark to ground. I found some schematics for coil packs and this isn't your old point and condenser system anymore. I won't say they are precisely 'tuned', but the circuits were designed and proven with plain sparkplugs.
(All of this is nearly gut feel and should be taken as such)
As a DD owner, I hate to make that conclusion because it means somewhere along the way I will need to change plugs in MN winter, and it is just so special when your tools are freezing cold.
The design of the coil pack really surprised me. We all know that the coil fires in pairs. I expected the pair to be simply connected internally. It isn't that way.
The coil pack floats between the two plugs and sends a + spike out one side and a - spike out the other side. I can't tell if the + and - alternate or if it is always that polarity.
But, it does mean that, if one chooses to use platinum plugs, they need to use double platinum or they will not get even wear.
That's the way it looks on paper. It may not matter at all, and someone who uses single platinum plugs will counter me with 15 years of explorer experience. I prefer experience. Can anyone state that they use single platinum plugs and they wear equally? I'd really like to know one way or the other.